1. Field of the Invention
This invention generally relates to an electronic package, and more particularly to an electronic package using wire bonding technique wherein the electronic package comprises a chip disposed on a substrate having a ground ring, a power ring, and at least a surfacemountable device connected across the ground ring and the power ring.
2. Description of the Related Art
An electronic package typically includes a circuitized substrate with one or more active devices attached thereon; packages including only one device are known as Single Chip Modules (SCM), while packages including a plurality of devices are called Multi Chip Modules (MCM). The active device is typically a chip commonly made of Silicon, Germanium or Gallium Arsenide.
As the speed of semiconductor devices increase, noise in the DC power and ground lines increasingly becomes a problem. To reduce this noise, capacitors known as decoupling capacitors are often used to reduce power supply noise which occurs due to change in potential difference between the ground voltage and the power-supply voltage supplied to the active device. The decoupling capacitors are placed as close to the active device as practical to increase their effectiveness. Typically the decoupling capacitors are connected to power and ground as close as possible to the active device.
FIG. 1 shows a conventional BGA substrate 100 with a chip 110 securely attached to the metal paddle 102 on the upper surface of the substrate 100. The upper surface of the substrate 100 is provided with a ground ring 104, a power ring 106, and a plurality of conductive traces 108. The ground ring 104 is predetermined for coupling to a source of the ground reference voltage. The power ring 106 is predetermined for coupling to a source of the power reference voltage potential. In order to suppress the power supply noise described above, several decoupling capacitors 120 are connected across the ground ring 104 and the power ring 106. Typically, the decoupling capacitors 120 are surface-mountable devices (SMD's) used in the so-called surface-mounting technique in which the capacitors 120 are directly secured to the ground ring 104 and the power ring 106 via two end contacts thereof.
However, when these capacitors are on the substrate at the package level, they hinder the space available for the wire bonding. This is because it is generally preferred to avoid contact between the bonding wires and the capacitors. Therefore, the bonding wires 130 connected between the chip 110 and the ground ring 104 (or the power ring 106) at the periphery of the decoupling capacitors 120 must keep away from the decoupling capacitors 120 thereby increasing difficulties and risks of wire bonding.